This compound, prepared from 1,1-dichloro-ethylene (A. E. Feiring, J. Fluorine Chem., 14(1), 7-18 (1979)) or from 1,1,1-trichloroethane (patent no. DE 2,137,806) contains as impurities unsaturated chloro or chlorofluoro compounds which are undesirable in the use of 1,1-dichloro-1-fluoroethane. The most inconvenient of these unsaturated impurities are 1,1-dichloroethylene and dichloroacetylene whose boiling points (31.7.degree. C. and 33.degree. C. respectively) lie very close to that (32.degree. C.) of 1,1-dichloro-1-fluoroethane.